Scheme to determine completion of directory operations for server recovery

摘要

In a fault-tolerant distributed file system, the server state needs to be reconstructed after the server restarts or when its function is taken over by another node. A crucial part of the server state is determining whether or not in-flight, directory-operations initiated by the clients have been completed. Described is a check-before-request scheme that solves this problem. A global lock is obtained on the directory or directories first. A check is made on the directories to see if the operation would succeed, and if so a request is made to the server for the operation. If the server were to fail during the execution of the operation, completion of the operation prior to failure can be determined by merely re-examining the directory contents.